As magnetic coupling pumps, for example, there is one disclosed in the following PTL 1.
This magnetic coupling pump is equipped with a closed impeller, and a casing that houses the impeller in such a way that the impeller is rotatable around a rotation axis and movable in an axis direction. The impeller has a columnar shaft portion centered on the rotation axis, and driven magnets formed from permanent magnets are provided within this shaft portion. The impeller are rotated integrally with the internal driven magnets by the rotation of driving magnets that are arranged outside the casing so as to face the driven magnets and are magnetically coupled with the driven magnets.
A portion of an inner casing surface forms an inner peripheral surface that is formed in a cylindrical shape around the rotation axis, and a portion of an outer impeller surface forms an outer peripheral surface that faces the inner peripheral casing surface and is formed in a cylindrical shape around the rotation axis. A gap is presents between the inner peripheral casing surface and the outer peripheral impeller surface, and the respective peripheral surfaces form dynamic pressure bearing faces.
Additionally, another portion of the inner casing surface forms a perpendicular inner surface that widens in a radial direction perpendicular to the rotation axis, and another portion of the outer impeller surface forms a perpendicular outer surface that faces the perpendicular inner casing surface in parallel at a distance therefrom in the axis direction.
That is, in this magnetic coupling pump, the impeller rotates within the casing where the inner casing surface and the outer impeller surface are in a state of non-contact.